Resin-acid ester-acetals of polyhydric alcohols



Patented July 25, 1950 RESIN-ACIDE'STER-ACETALS vor POLYHYDRIC ALCOHOLS:

Harry Burrell, Paramus, and Robert H. Barth, Ridgewood, N. J assignors to Heyden Chemical Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application November 13, 1944,

Serial N0. 563,310 x 11 Claims. (01. 2 -104) The present invention relates to new and novel chemical compounds and to compositions comprising said new compounds and synthetic rubbers, such as copolymers of diolefins and styrene and copolymers of diolefins and acrylonitrile. In one of its more specific aspects it relates toacetals of partial esters of certain polyhydric alcohols, such as the diabietic acid ester of pentaerythritol butyral, which are especially advantageous tackifiers and tack-imparting or tackifying softeners for synthetic rubbers. This application is a continuation-in-part of our prior copending application Serial No. v 525,592, filed March 8, 1944, which issued as Patent No. 2,446,257.

Synthetic rubbers, such as copolymers of buta-j diene and styrene (Buna-S or GR-S) and copolymers of butadiene and acrylonitrile (Buna-N, I-Iycar-OR, or GR-A) and the like, differ from natural rubber in many respects, especiallyin the quantities and types of compounding ingredients which must be incorporated therewith,

and in the compounding procedures which must be used to produce automobile tires and other useful articles therefrom. Carbon black, for ex ample, must be incorporated in greater quantities in synthetic rubber of the GR-S type than .in natural rubber to produce automobile tires, and

special grades of carbon black must be used for I the purpose. Different vulcanizing agents, softening agents and the like are also used.- Softeners are generally used with both natural and synthetic rubber but, when used with these synthetic rubbers, greater proportions are required and the effects produced may be generally different from those produced in natural rubber.

When natural rubber is milled with compound improve the plasticity of the mass without affect ing the tackiness substantially; for the most part they must be used in such quantities as to destroy at least partially what little inherent tackiness is possessed by the synthetic rubber. As a consequence, the industry has long sought softeners that improve the tackiness or coherence of s nthetic rubbers and permit it to be milled and treated in much the same manner as naturalrubher or substances which, when added to conven-y tional synthetic rubber, compositions, improve the tackiness of the resulting compositions, especially during milling.

It is a principal object of the present invention to providea tackifier for synthetic rubber compositions, such as those produced from copoly- A further object of the invention is to provide a material which may be used as both a softening and tackifying ingredient for compositions 7 comprising such synthetic rubbers.

Other objects and advantages of the invention, some of which are referred to more specifically hereinafter, will be apparent to those skilled in the art to which the invention pertains.

We have discovered that the foregoing objects are realized to a remarkable degree by the use of certain new andnovel compounds which we described in our-'copending application, Serial No. 525,592, filed March 8, 1944, which issued as Patent No. 2,446,257. These compounds are exemplified by pentaerythritol diabietate butyral, which may possibly as: r

* Abietyl-OH:C CHr-O and which is the reaction product of 2 mols of abietic acid (rosin), 1 mol of pentaerythritol and 1 mol of butyraldehyde; Other compounds of this type which possess these desirable properties may be prepared from other acids of the type of abietic acid, other polyhydric' alcohols, other a1- dehydes, and in other molecular proportions, as specified hereinafter.

The compoundsor products to which the present invention is specifically directed may be prepared generally by partial esterification of glycerol, pentaerythritol, a polypentaerythritol, or mixturesthereof, with abietic acid or a similar acid or a material, such as tall oil, containing a substantial proportion of such acids. This esterification may be effected by heating the two materials in the presence of a catalyst but it normally proceeds sufiiciently rapidly without a catalyst in the temperature range from approxi-:

mately to approximately 300 C. or somewhat higher. Catalysts which may be used, if

desired, are sulfuric acid, p-toluenesulfonic acid,

resinates and naphthenates of lithium, calcium,

be representable structurallystrontium, barium, zinc and cadmium and other soluble salts of these metals, as described in Burrell Patent No. 2,360,394, and the like. When pentaerythritol esters are being prepared, care should be exercised not to overheat the pentaerythritol before the esterification has "proceeded to a substantial extent, since overheating may result in the decomposition of the pentaerythritol with the formation of dark-colored products and undesirable byproducts. has been formed it is then reacted with an aldehyde to produce an acetal.

The reaction of the partialester with the aldehyde may be conducted by heating the'tWo materials together in the presence of an acid catalyst, such as oxalic acid, hydrochloric acid, sulfuric acid or the like. solvent such as toluene or a saturated aliphatic hydrocarbon or petroleum fraction to prevent foaming and to aid in removing the water formed in the reaction. "Asthe aoetaliz'ation proceeds, the reaction temperature may be "raised. Itis generally desirable to conduct th'e' 'acetalization in an apparatus provided with a reflux condenser, separator ortrap, and a return line,'and' toeffect the heating in the 'presenceof-t'oluene' or other solvent which'is 'ir'nmisciblewith water but which forms'an 'azeotrope witnw'ater; 'By

using such an apparatus and such a solvent, the reactants can be heated'under-gentIe reflux and the temperature "can be more readily controlled. In operating in this manner, theconde'nsed reflux liquid is collected in the separator or trap, the water is separatedtherefromperiodically, and the toluene is returned to'the'reaction mass. At the end of the acetaliza'tion' the solvent can'be removed by volatilizatlo'n, preferably at reduced pressure, that is, by vaeuuindistillation.

Instead of preparing thepartial ester by heating the acid and polyhydric alcohol together in the desired stoichiometric proportions a complete ester may be used as 'the'starting material; Thefcomplete ester may bealcoholized withglyC- erol, pentaerythritol or apolypentaerythritol, in-

the presence of catalysts, if desired, to form the partial ester. Thusp'entaerythritol tetra-abietate may "be reacted with pentaerythritol to produce pentaerythritol diabietate in the presence of catalysts such as are'disclosed in Burrell Patent No. 2,360,394.

Although, in the preparation of compounds for use as tackifiers from pentaerythritol, in accordance' with the process of the presentin'vention, it is generally desirable to have two of the hydroxyl radicals 'ofpentaerythritolesterified by abietic acid or its equivalent'aiid the remaining two acetalized by the aldehydefthese proportions maybe varied considerably. With pentaerythritol, satisfactory products "may'beobtained from the reaction of one molecular-equivalent to three molecular equivalents of abietic aoid and the acetalization of the remainin hydroxyl groups. With dipentaerythritol, whichcontains six hydrox-yl groups per molecule, from one to five of the hydr'oxyl groups may be esterified with abietic acid and the 'remaininghydroxyl groups may be acetalized. When glycerol is used as the starting materiaL either one or two hydroxyl groups may be acetalized.

The composition of the products which are formed has not been definitely established but obviously they are somewhat more complex than indicated by the probable structure of pentaerythritol diabietate butyral as "given hereinabove. The products may be pure compounds or mix- After the partial ester- It is desirable to add an inert tures of pure compounds, in which there may be cross-linkages between the original polyhydric alcohol nuclei through the acetal group. A possible compound, for example, which has such cross-linkages and also has the same empirical butyral.

The order of the esterification and acetalization may be reversed but esterification prior to 'acetelaziation is recommended and preferred because of its simplicity.

Instead of using pure abietic or sylvic acid in the production of the tackifiers or tackifying softeners of the present invention, rosin'of various grades or degrees of purity may be used. Pure abietic acid has an acid number of 162, whereas Grade E Wood rosin, which may also be used as a startin material, may have an acid number as low as 110. Of course, compensation for these differences should be made, for example, by using these acid numbers in computing the quantities of the polyhydric alcohol to be used for esterification. Tall oil or tallol, which is rich in resin acids, containing as much as 40% by weight of these acids which include substantial amounts of Steeles abietic acid and d-pimaric acid, may also be used to replace abietic acid, either partially or completely. Other acids of the type of abietic acid which may be used for partial or complete replacement of abietic acid are levopimaric acid, d-piamric acid and Palkin acids.

Glycerol, pentaerythritol, polypentaerythritols and mixtures thereof are the preferred polyhydric alcohols for use in producing the compounds of the invention. Dipentaerythritol and tripentaerythritol are two of the po'lypentaerythritols which have been definitely isolated and identified. Pleopentaerythritol, one of the products that can be isolated from the condensation of formaldehyde and acetaldehyde in the presence of an alkali, and which has a melting point of230 to 240 C. and a hydroxyl content of 33%, possesses some of the attributes of a, pure compound, but is a mixture of dipentaerythritol and tripentaerythritol with other hydroxylated products. Tetrapentaerythritol and higher polypentaerythritols have been postulated at the present time.

The polyhydric alcohols which may be used for the production of tackifying compounds in accordance with the invention are relatively restricted. Thus, ethylene glycol, propylene glycol, diethylene glycol and the like do not produce compounds which exhibit to any substantial extent the desirable properties possessed by acetals of abietic esters of glycerol, pentaerythritol and polypentaerythritols. The effect of using a diethylene glycol diabietate butyral in a butadienestyrene copolymer is illustrated in the preparation entitled Comparison Composition 1 hereinafter.

The aldehydes which may be used in the production of the acetals of abietic acid esters of polyhydric alcohols in accordance with the process of the invention are formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde and other aliphatic aldehydes having up to and including those in which all the hydroxylgroups of the polyhydric alcohol have been combined, that is, some with abietic acid or its equivalents and some with an aldehyde. v However, compounds with a free hydroxyl group or mixtures containing some compounds having uncombined hydroxyl groups, as well as compounds of this type in which one or more of the hydroxyl groups has been esterified by acetic acid or other aliphatic or aromatic acids, may also be used. v Although the acetals of abietic esters of polyhydric alcohols which are described here'in are especially adapted for use with synthetic rubbers of the-types represented by copolymers of butadiene and styrene (GR-S and copolymers of butadiene and acrylonitrile (GR-A), they may beused generally with all synthetic rubbers which are copolymers of a 1,3#butadiene hydrocarbon and another unsaturated compound which contains a, CH2=C: group and is copolymerizable therewith. b

In the "following examples, which are not to be construed as limitative of the invention, are described methods of preparing suitable compounds for use as tackifying agents in accordance with the process of the invention. Following these examples are illustrated typical compositions containing synthetic rubber and these tackifying agents and results of vulcanizing or curing tests of such compositions.

EXAMPLE l.PENTAERYTI-IRITOL DIABIETATE BUTYRAL A mixture of 2000 parts of rosin (acidnumber:l62) and 417 parts of technical pentaerythritol (hydroxyl value:46.5%; combining weight:36), Was heated for two hours at 280 C. under an atmosphere of carbon dioxide. The mixture was then cooled to approximately 80 C. and 236 parts of butyraldehyde were slowly added. During the slow addition of the butyraldehyde, concentrated hydrochloric acid was added dropwise until 55 parts had been added. Then 250 parts of toluene were added and the mixture heated gently under reflux with progressively increasing temperature, in an. apparatus in which the reflux condenser was connected to a trap in which the condensed toluene-water azeotrope collected. The water was separated and removed periodically from the trap and the toluene was returned to thereaction mixture. After no further substantial quantity of water collected in the trap, the toluene was removed from the reaction mass by vacuum distillation.

The product was a heavy oil which solidified on cooling to a hard, brown, glassy and brittle substance having a low softening point (60 C. or higher).

Methods of compounding this product with copolymers of butadiene and styrene (see Composition 1 hereinafter) and 'butadiene and acrylonitrile (see Composition 2 hereinafter) are described hereinafter and the effects produced in such copolymers are tabulated in Table 1.

"EXAMPLE 2.-PENTAERYTHR1T0L DIABIETATE B TYRAL A mixture of 900 parts of resinous pentaerythritol diabietate and 90 parts of butyraldehyde was heated to 105 C. Then 1.5 parts of oxalic acid were added and the mixture was heated at approximately 100 C. for two hours. Mostof the water formed in the reaction was removed during thisperiod. To the reaction mass were then added 100 parts of toluene and the mixture was heated under gentle reflux in an apparatus similar to that described in Example 1, in such manner that the water which distilled .over as an azeotrope with toluene was separated from the toluene and periodically removed. After about five hours of heating, during which time the temperature rose from 100 to 150 0., the toluene was removed together with the remaining water.

. The resulting product was substantially identical with that formed in Example 1.

EXAMPLE 3.-PENTAERYTHRITOL DIABIETATE BENZAL Pentaerythritol diabietate benzal, the benzal of the partial abietic acid ester of pentaerythritol, was prepared by reacting pentaerythritol with sunicient wood rosin to esterify approximately one-half of the hydroxyl groups of the pentaerythritol by abietic acid. The mixture of rosin and pentaerythritol was heated slowly to 280C. in 3 hours. An atmosphere of carbon dioxide gas was maintained over the batch to prevent the formation of oxidation products that darken the color.

The resulting diabietate of pentaerythritol was then reacted with suflicient benzaldehyde to acetalize the remaining hydroxyl groups of the pentaerythritol by heating the mixture together with a small proportion of hydrochloric acid under gentle reflux for 1 hour. A small amount of toluene, was added prior to heating the reaction mixture in order to suppress foaming. The unreacted benzaldehyde, water and toluene were then distilled from the batch by heating at 200 C. for 30 minutes.

The product was a hard, brown-colored, homogeneous friable solid that retained a slight odor of benzaldehyde. The yield was 88% of the theo-- retical. H

' The effects produced by using this product in the compounding of a synthetic rubber consisting of a butadiene-styrene copolymer (Composition 3) ,are tabulated in Table 2 hereinafter.

a EXAMPLE 4.-GLY0ER0L ABIETATE BUTYRAL 96 C. The water of reaction, unreacted butyraldehyde and unreacted glycerol were then removed by vacuum distillation at a pressure of 5 mm., during which the temperature rose to C.

The product was a dark brown-colored viscous liquid that retained a slight odor of butyraldehyde.-

The effects produced by incorporating this product in a butadiene-styrene copolymer (Composition 4) are tabulated in Table 2 hereinafter.

COMPARISON EXAMPLE 1.-DIETHYLENE GLYcoL DIABIETATE BUTYRAL The diabietate of diethylene glycol was prepared by heating together at 220 C. for 3 hours a mixture consisting of 318 grams of diethylene glycol and 1035 grams of wood rosin, color N (acid value=162) The diabietate of diethylene glycol was then heated under reflux for 4 hours with a stoichiometric excess of butyraldehyde in the presence of 20 grams of concentrated hydrochloric acid. The unreacted butyraldehyde and water of reaction were then distilled off at a pressure of 5 to mm.

The product was a viscous brown-colored liquid having a slight odor of butyraldehyde.

i Results obtained on compounding this product with a butadiene-styrene copolymer (Comparison Composition 1) are tabulated hereinafter in Table 2.

EXAMPLE 5.-HALF-ABIETATES or MIXED FoRMALs .AND BUTYRALS or PENTAERYTHRITOL AND PoLY- RENTAERYTHRITOLS In this example is used a mixture of partial formals of pentaerythritol and polypentaerythritols that was obtained as a byproduct in the manufacture of pentaerythritol by the condensation 3 of formaldehyde and acetaldehyde in the presence of an alkaline catalyst, which was recovered in accordance with the process described in the application for Patent Serial No. 484,242, filed April 23,1943, by Karl A. Fisher and Harry Burrell, now abandoned, and which is therein referred to as B-liquor.

To 495'parts by weight of the above mixture of formals was added 2000 parts of wood rosin, Grade N, which is sufficient to esterify approximately one-half of the hydroxyl equivalent of the mixture, and the mixture was heated for 3 hours at 280 C. The resulting product was then cooled to approximately 100 C. and 240 parts by weight of butyraldehyde and 5 parts by weight of concentrated hydrochloric acid E01) were added. This mixture was then heated under total reflux for 4 hours. The unreacted butyraldehyde and volatile products were removed by distillation at a pressure of several millimeters.

The .product was a light amber-colored solid that was tacky and very cohesive.

Incorporation of the product into butadienestyrene copolymers (Composition 5) and the effects produced therein are tabulated in Table 3 hereinafter.

EXAMPLE 6.QUARTERABIETATES or MIXED FOR- MALS AND BUTYRALs or PENTAERYTHRITOL AND POLYPENTAERYTHRITOLS Example 5 was repeated but the proportions of reactants were varied so that only half as much rosin was used for the esterification of the mixture of partial formals of pentaerythritol and polypentaerythritols. The remaining hydroxyl groups were acetalized with butyraldehyde.

The effectiveness of this product as compared with that of Example 5 when used in butadienestyrene copolymers (Composition 6) is shown in Table 3 hereinafter.

EXAMPLE 7.TALL-O1L ESTERS or MIXED FORMALS AND BUTYRALS or PENTAERYTHRITOL AND POLY- PENTAERYTHRITOLS A mixture of partial formals of pentaerythritol and polypentaerythritols such as was used in Ex- Acid number=163 Resin acids- 45.2% Fatty acids=47.3% Combining weight=345 Sterols, etc.=7.0% Moisture=0.6 Ash=0.35%

One hundred seventy (1'70) parts by weight of the tall oil were mixed with 748 parts by weight of the mixture ofpartial formals and heated for 2 hours at 275C. The product was then reacted with butyraldehydein excess and recovered as in Example 5.

The product consisted of a dark brown-colored viscous liquid.

The effects produced on incorporating the product into a butadiene-styrene copolymer (Composition '7) are tabulated in Table 3.

In general, pentaerythritol diabietate butyral and related compounds, to which the present specification is directed, are hard, brittle resinous solids which are generally brown in color, have low melting points or ranges, and low acid numbers (approximately 10 or less). They are soluble in various solvents, such as acetone, xylene, benzene and toluene, and are compatible with linseed oil, petroleum. oils, natural and synthetic rubbers and with natural and synthetic resins. They are also compatible with rosin and waxes and may be used as ingredients in the production of sealing wax and similar compositions.

When added to synthetic rubber compositions comprising such materials as butadiene-acrylonitrile and butadiene-styrene copolymers in amounts up to approximately 2 to 3% by weight of the copolymer, pentaerythritol diabietate butyral and related compounds greatly improve the milling characteristics. In amounts up to approximatel 40% by weight of the copolymer, the uncured synthetic rubber compositions possess considerable tack and show long fingers but the cured rubber will not be sticky and will retain good nerve. With greater amounts, in excess of approximately 40% by weight of the copolymer, pronounced tack, softening and plasticizing are produced and this tack is retained to a considerable extent after curing or vulcanization, These effects are produced without other significant changes in the properties of the rubber compositions, but the curing time of the composition is generally retarded slightly.

In using pentaerythritol diabietate butyral and the related tackifying compounds of the present invention in the production of synthetic rubber compositions, conventional compounding procedures may be adopted. Except for providing for slightly increased curing periods, no substantial changes in compounding or curing procedures are required. Generally it is desirable to incorporate the tackifying compound directly with the copolymer on the rubber mill by breaking down the copolymer at a suitable temperature, for example, 38C. F.), and adding the tackifying compound thereto. The additional compounding ingredients may subsequently be incorporated or blended therein. The temperature at which the milling is most advantageously conducted Will be dependent upon the amount of tackifying compound that is added. In some cases it may be necessary to cool or chill the rolls below normal operating temperaturebecause of the softness of the composition.

Preferred methods of fying compounds of the invention and typical synthetic rubber compositions containing such compounding the tacki- 1i. -taerythrito1 diabietate butyral were also tested for comparison. 7

The results are as follows:

Table 1 Modulus, pounds per Ultimate Minutes square inch, at per Tensile Ultimate Show I Product I Cure cent Elongation Strength, Elonga- Dummeter at 1 pounds tion, H dn 300 F; per square per cent M 958 v 300% 500% 700% inch Butadiene-Styrene Itubber-Pentaerythritol Diabietate I j Butyral OIHDOSltlOIl 1) o 1: 40 90 0 Butadiene-Acrylonitrile Rubber-Pentaerythritol Dia-I g %g bietate Butyral (Composition 2) 60 3:140 670 70 825 480 50 Butadiene-Styrene Rubbet-Dibutyl Phthalate 1, 030 460 55 v 60 690 1, 145 440 I 55 15 160 320 530 770 940 Butadiene-Acrylonitrile Rubber-Dibutyl Phthalate 30 200 500 705 1, 150 990 I A so 330 650 1,010 I 1, 7 25 920 compounds are illustrated in the examples which COMPOSITION 3 follow I COMPOSITION 1 One hundred (100) parts by weight of a butadiene-styrene copolymer (GR-S) rubber were rolled on a rubbermill at a temperature of 38 C. (100 F.). While being thus subjected to break down, 25 parts by weight of the pentaerythritol diabietate butyral tackifying compound prepared as described in Example 1 were added in small proportions during the milling. The composition milled easily and became tacky during the mixing. After the tackifying compound had been thoroughly distributed and incorporated, a, mixture of 50 parts by weight of channel black and, 5 parts by weight of zinc oxide, 1.25 parts by weight of sulfur powder (flowers of sulfur) and 1.25 parts by weight of a commercial accelerator COMPOSITION v ,p The foregoing example was repeated but, instead ofusing a 'butadiene-styrene copolymer,

A-jbutadiene-styrene copolymer. (GR-S). composition was prepared from the following:

tabulatedin Table Zhereinafter.

COMPOSITION 4.-

A composition was prepared exactly as Com- 1 position 3 except that the glycerol abietate butyral, of Example, 4 was used instead of pentaerythritol diabietate benzal.

Physical characteristics of vulcanized products prepared from this composition are tabulated in Table Zhereinafter. a 1.

the composition was prepared from a butadieneacrylonitrile copolymer (GR-A) sold under the trade-name I-Iycar OR-15. The tackifierwas readily incorporated in this manner and theprodnot before curing had excellent tack but was free from tack after vulcanization.

Physical characteristics of the vulcanized products prepared from this composition are tabulated in Table 1 hereinafter.

CURING TESTS OF COMPOSITIONS 1 AND 2 COMPARISON COMPOSITION 1 A composition wasprepared exactly as Composition 3 except that the diethylene glycoldiiabietate butyral of- Comparison Example 1 was substituted for pentaerythritol diabietate benzal, weight for weight.

Physical properties of cured products prepared from this composition are tabulated in Table 2 hereinafter.

CURING TESTS OF COMPOSITIONS 3 AND 4 ANDCOMPARISON COMPOSITION 1 Table .2

Modulus, pounds per Ultimate Minutes square inch, at per Tensile Ultimate Show Product Compounded with GR-S g cent Elongation 5232 gg Durometer 300 F." per square per cent Hardness 300% 500% 700% inch l 335 670 950 1, 330 870 55 Pentaerythntol Diabletate Butyral (Compos1tion 1) 30 490 890 1, 380 1, 570 780 55 60 680 l, 140 1,640 690 60 15 500 880 1, 400 1, 875 800 65 Pentaerythritol Diabietate Benzal (Composition 3). 30 760 1, 310 1,785 600 60 i 60 760 1, 330 l, 770 590 60 15 545 1, 000 1, 530 1, 780 770 55 Glycerol Abietate Butyral (Composition 4) 30 800 1, 340 1, 600 530 60 1 60 510 ,00 1, 450 1, 810 775 50 D1etl1ylene; Glycol Diabietate But'yral (Comparison 15 800 1, 520 1, 530 500 55 Composition 1) .4 30 706 1,360 1,530 495 55 I 5 60 745 1, 370 l, 430 500 55 In all cases, except that of Comparison Composition 1, which is that prepared from a butadiene-styrene copolymer and diethylene glycol diabietate butyral, the tackifying ingredient was incorporated very readily by the procedure described and all the compositions possessed excellent tack during milling except Comparison Composition 1. Diethylene glycol diabietate butyral is quite unsatisfactory for use as a tackifying ingredient for synthetic rubber in accordance with the process of the present invention.

In all compositions, including Comparison Composition 1, no tackiness or only slight tackiness remained in the respective products after curing at 300 F. for the specified intervals.

From the above results it will be noted also that the curing time is slightly accelerated in the case of Composition 3 (that made with the benzal COMPOSITION 7 The tall-oil esters of mixed formals and butyrals of pentaerythritol and polypentaerythritols whose preparation is described in Example 7 were substituted weight for weight for the tackifying ingredient used in Composition 3 and in other respects the composition was prepared as described in Example 3.

CURING TESTS OF COMPOSITIONS 5, 6 AND '7 The results of curing tests of the three foregoing compositions, which were conducted in the same manner as the curing tests of Compositions 1 and 2, are tabulated in Table 3. For comparison, the results obtained in such tests with Composition 1 1 are included.

Table 3 l Modnlus, pounds per Ultimate Minutes square inch, at per Tensile Ultimate Shore Product Compounded with GR-S g cent Elongatlon 33E53 gg?" Durometer 300 F. per square per cent Hardness 300% 500% 700% inch 1, 330 870 Pentaerythritol Diabietate Butyral (Composition 1) 1, 570 780 55 1, 640 590 p v 2, 600 910 Half-Abietates of B-Liquor Butyrals (Composition 5) 2, 530 750 2, 730 560 70 Quarter-Abietatesof -B-Liquor Butyrals' (Composi- 6) 1, 680 550 60 Tall-Oil Esters of B-Liquor Butyrals (Compost 1 of pentaerythritol diabietate) and that curing of the others, except Comparison Composition 1, was slightly retarded by the presence of the tackifying ingredient in the compositions.

COIWPOSITION 5 COMPOSITION -6 I The quarter-abietates of mixed formals and butyrals of pentaerythritolandpolypentaerythritols of Example 6 were substituted weight-for weight for the tackifying ingredient used in Composition 3 and in other respects the compositionwas prepared as described. inrExamp'le ,3.

In all the above compositions (1, 5, 6 and 7) the tackifying ingredient was incorporated very readily by the procedure described and all the compositions possessed excellent tack during milling. No tackiness or only slight tackiness remained in the respective products after curing at 300 F. for the specified intervals, although the sample of Composition '7 that was cured for 60 minutes was slightly but definitely tacky. Increasing the time of curing appears to favor development of after-curing tackiness in synthetic rubber composition comprising the tackifiers of the invention.

In all the above compositions (1, 5, 6 and '7) the curing time was slightly retarded by the addition of the tackifiers, being least retarded by the tall-oil esters of mixed formals and butyrals of pentaerythritol and polypentaerythritols (Composition 7);

Although the foregoing description comprises preferred embodiments of the invention, it is to be understood that the invention is not limited thereto and that modifications and variations may be made therein without departing substantially from the principles or scope of the invention. The invention is to be limited solely by the appended claims.

We claim:

1. An ester-acetal of a polyhydric alcohol selected from the group consisting of glycerol, pentaerythritol and polypentaerythritols, in which at least two but not all of the hydroxyl groups of the alcohol have been acetalized in pairs by an aldehyde selected from the group consisting of aliphatic aldehydes having not more than eight carbon atoms in the molecule and benzaldehyde and at least one of the other hydroxyl groups has been esterified by a resin acid selected from the group consisting of d-pimaric acid, levopimaric acid, abietic acids and Palkin acids.

2. A. composition comprising the reaction product of an aldehyde selected from the group consisting of aliphatic aldehydes having not more than eight carbon atoms in the molecule and benzaldehyde with a partial abietic acid ester of a polyhydric alcohol selected from the group consisting of glycerol, pentaerythritol and polypentaerythritols that has been partially but not completely esterified by the abietic acid.

3. A composition comprising the reaction product of at least one molecular proportion of an aldehyde selected from the group consisting of aliphatic aldehydes having not more than eight carbon atoms in the molecule and benzaldehyde with one molecular proportion 'of a partial abietic acid ester of pentaerythritol in which at least one but not more than three of the hydroxyl groups of the pentaerythritol have been esterified by abietic acid.

4. An ester-acetal of pentaerythritol in which two of the hydroxyl groups of the pentaerythritol have been 'acetalized by an aldehyde selected from the group consisting of aliphatic aldehydes having not more than eight carbon atoms in the molecule and benzaldehyde and at least one of the remaining hydr-oxyl roups has been esterified by abietic acid.

5. An ester-acetal of pentaerythritol in which two of the hydroxyl groups of the pentaerythritol have been acetalized by an aliphatic aldehyde having not more than eight carbon atoms in the Y 14 molecule and at least one of the remaining hydroxyl groups has been esterified by abietic acid.

6. An ester-acetal of a polyhydric alcohol selected from the group consisting of glycerol, pentaerythritol and polypentaerythritols, in which at least two of the hydroxyl groups of the polyhydric alcohol have been acetalized in pairs with butyraldehyde and at least one of the remaining hydroxyl groups has been esterified by abietic acid.

7. Pentaerythritol diabietate butyral, which is a hard, brown, glassy and brittle substance having a softening point of approximately C.

8. An ester-acetal of pentaerythritol in which two of the hydroxyl groups of the pentaerythritol have been esterified by benzaldehyde and-at least one of the remaining h droxyl groups has been esterified by abietic acid.

9. Pentaerythritol diabietate benzal, which is a hard, brown, friable solid.

10. A. composition comprising the reaction product of at least one molecular proportion of an aldehyde selected from the group consisting of aliphatic aldehydes having not more than eight carbon atoms in the molecule and benzaldehyde with one molecular proportion of a partial abietic acid ester of dipentaerythritol in which at least one but not more than five of the hydroxyl groups of the dipentaerythritol have been esterified by abietic acid.

11. An ester-acetal of dipentaerythritol in which at least two of the hydroxyl groups have been acetalized in pairs with butyraldehyde and at least one of the remaining :hydroxyl groups has been esterified by abietic acid.

HARRY BURRELL. ROBERT H. BARTH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,005,499 Hill June 18, 1935 2,311,781 Scrutchfield Feb. 23, 1943 2,324,980 Kilbourne July 20, 1943 2,446,257 Barth Aug. 3, 1948 FOREIGN PATENTS Number Country Date 760,126 France Feb. 16, 1934 

1. AN ESTER-ACETAL OF A POLYHYDRIC ALCOHOL SELECTED FROM THE GROUP CONSISTING OF GLYCEROL, PENTAERYTHRITOL AND POLYPENTAERYTHRITOLS, IN WHICH AT LEAST TWO BUT NOT ALL OF THE HYDROXYL GROUPS OF THE ALCOHOL HAVE BEEN ACETALIZED IN PAIRS BY AN ALDEHYDE SELECTED FROM THE GROUP CONSISTING OF ALIPHATIC ALDEHYDES HAVING NOT MORE THAN EIGHT CARBON ATOMS IN THE MOLECULE AND BENZALDEHYDE AND AT LEAST ONE OF THE OTHER HYDROXYL GROUPS HAS BEEN ESTERIFIED BY A RESIN ACID SELECTED FROM THE GROUP CONSISTING OF D-PIMARIC ACID, LEVOPIMARIC ACID, ABIETIC ACIDS AND PALKIN ACIDS. 